Diffusion transfer photography is known in the art today and will not be further discussed hereinafter. For details, references can be made to A. Rott, E. Weyde, Photographic Silver Halide Diffusion Processes, (Focal Press, 1972); J. Sturge, V. Walworth, A. Shepp, Imaging Processes and Materials: Neblete's Eighth Edition, Chapter 6, Instant Photography and Related Reprographic Processes (Van Nostrand Reinhold, 1989); G. Haist, Modern Photographic Processing, Vol. 2, Chapter 8, Diffusion Transfer, (John Wiley and Sons, 1979); T. H. James, The Theory of Photographic Process, Fourth edition, Chapter 6, (Macmillan, 1977), etc.
In the diffusion transfer process, many kinds of photographic materials can be prepared. Among commercial photographic light-sensitive materials are color instant photographs (e.g., FI-800, FP100C, available from Fuji Photo Film Co., Ltd.) and black-and-white instant photographs (e.g., FP3000B, EP400B, available from Fuji Photo Film Co., Ltd.). Any of these photographs is characterized by a structure in which an alkaline processing composition, e.g., a high viscosity or low viscosity alkaline processing composition containing a developer, is developed between two supports so that a transfer image can be obtained.
If the thickness of the processing solution developed between the two supports is too great, the various elements swell too much, increasing the diffusion distance of image-forming substances and hence retarding the finish of image formation (impairing the instantaneity). Thus, an image which looks blur as a whole (not sharp) is given. On the contrary, the reduction in the thickness of the processing solution developed between the two supports is advantageous in that the time required for the formation of an image is reduced and a sharp image can be obtained. However, it is also disadvantageous in that the amount of a developing agent and other components supplied into the light-sensitive material runs short and unevenness of the support (unevenness caused by fiber grain in the case of paper support) causes nonuniformity in the supplied amount of the processing solution, resulting in uneven development that leads to unevenness in image. In order to overcome these difficulties, various approaches have been considered such as change in the kind of fiber in the paper support and calendering of the support. However, these approaches are not sufficient to produce an ultrahigh smoothness support having a smoothness as high as 0.5 .mu.m or less on an industrial basis. In order to reduce the unevenness of image density due to the unevenness of the paper, the review of the light-sensitive element or image-receiving element may be sufficiently worth considering. However, this approach is not sufficient to overcome the foregoing difficulties without impairing various performances.
Further, JP-A-59-171159 (The term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses an approach which comprises the use of a polyester film. This approach exerts a sufficient effect of eliminating unevenness. However, this approach cannot entirely substitute for the prior art because it leaves much to be desired, i.e., it lacks the texture inherent to conventional photographs (plane looking, touch), is easily scratched at corners and makes fingerprints prominent. This approach is further disadvantageous in that it adds to the production cost.
The present invention is intended to obtain a photographic product which provides a sharp image that is less subject to image unevenness While maintaining a texture inherent to conventional photographs.
EP0507489A1 discloses a support for photographic paper comprising a polyester and titanium oxide coated on at least emulsion side of a raw paper. However, as can be seen in the expression "on the surface on which an emulsion is to be coated", EP0507489A1 is intended for the conventional type of photographic light-sensitive materials (e.g., color paper) but doesn't suggest effects on and application to diffusion transfer photography, particularly peel apart type instant photographs comprising an image-receiving sheet on which no emulsion is coated.
Further, the foregoing instant photography is characterized in that it is free from a procedure for removing a waste developing agent and alkali (rinsing process) and thus involves a process for neutralizing a high activity processing solution by lowering the pH thereof at the completion of development to give a low activity processing solution. These photographic materials need to be so hydrophobic that they are impermeable to an alkaline solution at the initial stage of processing. To this end, the foregoing instant photography mostly involves a production process for coating a nonaqueous solution. The coating in the form of nonaqueous solution can be hardly fixed after coated, possibly impairing the uniformity of the film. In order to overcome this difficulty, the coating is usually dried at a temperature as high as 80.degree. C. to 110.degree. C. in the art. However, in the case of a paper support comprising a raw paper of common use laminated with a polyolefinic resin (in most cases, polyethylene or polypropylene is used), which can easily soften, a slight amount of bubbles entrained in the raw paper or polyolefinic resin expand with the rise in the temperature and then penetrate or burst in the softened polyolefinic resin. This paper support is also disadvantageous in that the dimensional stability thereof is impaired by the shrinkage of the resin at a high temperature. In order to cope with these problems, the lowering of the drying temperature may be considered. However, this approach requires a longer drying zone. Further, the coating solution may comprise a dispersion of latex or the like so that the latex is fused to the paper during the drying process to form a continuous film. This approach is often advantageous in performance and cost (due to the absence of organic solvents). However, it has been keenly desired to make the resin laminate dryable at high temperatures without causing any problem to form a better continuous film.